Apparatus for shortening electric waves.



GfFERRARI & M. PIZZUTI. APPARATUS FOR SHORTBNING ELECTRIC WAVES.

APPLICATION IILED APR.14, 1910.

1,000,248. Patented Aug. 8, 1911.

2 SHEETS-SHEET 1.

G. FERRARI & M. PIZZUTI. APPARATUS FOR SHORTENING ELECTRIC WAVES.APPLICATION FILED APB..14, 1910.

' 1,000,248, Paten tedAug. 8,1911.

2 SHEETS-SHEET 2.

. circuit, it will be ineffective if in its neigh UNITED STATES PATENT.OF E CARLO FERRARI AND MICHELE PIZZUTI, 0F Harms," ITALY.

APPARATUS FOR snon'rnnms EIIEGTRIC. wavns.

Specification of Letters Patent.

Application flied April 14 1910. 'Serial No. 555,487.

Patented Aug. 8, 1911.

paratus for protecting electric installations from excessive accidentalvoltages arising from any cause.

It is known for instance that atmosphenc discharges which are generallyof an oscil- 'latory nature, produce by electrostatlc andelectromagnetic induction, oscillatory currents of high frequency andvoltage in electrical conductors, which currents are propagated bywaves. Whether these zdlsturb ances are ordinarily induced equally overall the conductors of one and the same cir- --cuit, or by thereflections at the points where the reactances and the capacities areconcentrated, it is certain that they can produce stationary wavesespecially if the conditions of resonance of the whole or part of thecircuit are satisfactory. It is these stationary waves which are themost dangerous for electrical installations because they allow of thegreatest amplitudes of the po tentials. They have also the greatestdudischargers uncertain. The greatest difficulties in the way ofprotection are as is well known, due to the fact that whatever thenature of the discharger placed in the borhood there should occur a nodeof the stationary wave of the potentials. In prac-.

tice, a greater protection of the installation is obtained by increasingthe number of dischargers included in the line, or in alightning-arrester which is combined or not with variousself-inductions. ing to the theory stationary waves of high frequencyoccurring in conductors, are the shorter the greater the capacity andself-induction of the line, if there be inserted in series with theconductor,- an apparatus of short length for which the product of theinductance and capacity per unit of length is much greater than theproduct of the inductance and capacity of the line per unit per length,then any wave on the conductor will become reduced in length even to thelength of the apparatus, and further, if the relation between theconstants of the con- Now, since accord-- ductor and that of theapparatus are maintained constant, the stationary Wave will not becomesubstantially modified by being shortened.

The present applicants have discovered that the successive nodes of astationary wave divide the conductor into sections for which the productof the inductance and the capacity has the same value. To the squarerootof the product of the self-induction and capacity of the apparatus,viz.,

- /L.Ca,

there may be given the value that corresponds to the entire length of astationary wave. In this case the values of the potentials correspondingto one wave will appear along the outer surface of the said apparatus.If now the apparatus be provided with multiple discharge gaps along thewhole of its surface that is traversed by the line current, the regularoperation of the apparatus will beinsured, because all the values of thepotentials of the wave will be obtained on the surface of the a paratus,and consequently the respective ischarge gaps will be found tocorrespond necessarily with the maximum potentials of the wave. This isequivalent to the installation of a very large number of discharge gapsover the equivalent length of the line, and the objection above referredto that the discharge gap will remain inefiective if a node of thestationary wave of the potentials occurs in its neighborhood, willthereby be overcome.

By calculation it will be found that with capacities constituted solelyby masses of metal, the object of the invention will not be attained,unless the dimensions are enormous, and therefore it is necessary tohave recourse to true capacities formed by two armatures separated by adielectric.

On the outside of the condenser there are provided multiple dischargegaps arran ed in pairs opposite one another. One hal of these areconnected to the outer armature, and the other half which are carried byinsulating supports may be connected to earth through the intermediaryof suitable resistances. The self-induction device is likewise furnishedwith discharge gaps.

According to one form of construction the apparatus comprises aself-induction coil formed of various elements wound on a dielectricwhose inner surface is covered by a metal armature, several pairs ofdischarge gaps being provided along the outer metallic winding and theinner armature being connected-to earth.

The accompanying drawings illustrate by way of example five typicalconstructions of apparatus according to this invention.

' Figural is an elevation of the type of the improved apparatus suitablefor installations in which the normal potential may rise to 1,000 volts.Fig. 2 shows in elevation and in plan the type of the improved apparatussuitable for installations working up to 10,000 volts. Fig. 3 shows insectional elevation and in plan the type of the improved apparatussuitable for installations working up to 80,000 volts. Fig.4 shows inside elevation partly in section and in end elevation, the type of theimproved apparatus in which the capacity and the self-induction deviceare contained in one and the same apparatus, and Fig. 5 is adiagrammatic view of the general scheme of connections.

Referring more particularly to Fig. 3 the improved apparatus is composedof two metal envelops a and b separated from each other by a partitionof porcelain 0 which acts also as an insulator for the line d. The wholeforms a bell-shaped condenser the outer lining of'which is connected tothe line and the inner lining to earth. The apparatus further comprisesfour pairs of dischar e gaps of the horn type arranged along a he icalline around the condenser in the manner shown, each pair of dischargingwings having one of its wings, viz., the discharging point It carried bya foot arranged on the outer lining and the other wing, viz.,

the discharging point g supported by a radial arm 71 which is carried bythe iron support y and is connected to the inner lining through saidsupport and through a metallic connection (not shown) between the latterand the inner lining of the condenser, the support 9' being connectedalso to earth.

The condenser formedby the metal envelops a and b and by the insulator ois mounted on the support j and fixed thereto through the intermediaryof a double bayonet joint formed on the one hand by an inner projectionor flange c, on the insulator c which flange extends for about half theperiphery of the insulator, and on the other hand by two sector shapedmetal plates Z and m which are screw-threaded on to the support glass)formed with bell-shaped projections p and provided with an inner metallining g which is electrically connected with the metallic support ofthe apparatus, (the support I combined elements itself being in its turnconnectedto earth,)

and with an outer metal winding r forming part of the line. A certainnumber of such (in the drawing four) of self-induction and capacity areinserted between the line and the installation to be protected and areconnected in series with one another, the connection between twoadjacent windings 1" being carried over an insulator .9 provided with ametallic cap having attached thereto a discharge wing IL. Opposite eachwing 72 there is provided a Wing 9 attached to a metallic cap which ismounted on an insulator t and is connected to earth e directly orthrough the intermediary of a resistance (not shown) according to thetension of the line.

Referring now to Fig. 5 which is a diagrammatic illustration of theelectrical connections when the apparatus shown in Figs. 1 to 3 areused, d represents the line, which is connected to the outer armature ofthe condenser, e the earth connection leading from the inner armature ofthe condenser, I

h g the discharging wings described in connection with Fig.- 3, uinductive coils arranged in series with one another and with thecondenser, 71., discharge wings metallically connected to theconnections between said resistances, and g discharge wings connected toearth 6, directly or through the intermediary of a resistance Raccording to the tension of the line.

The present applicants have obtained results which have clearly provedthe efficiency of this invention, the improved apparatus having operatedin an effective manner to discharge excessive potentials produced by thephenomena of resonance arising from various causes.

Having now fully described our said invention, and the manner in whichthe same is to be performed, what we claim and desire to secure byLetters Patent of the United States is:

1. An improved apparatus for protecting electric installation fromexcessive accidental voltages comprising in combination aself-induction, a capacity, and discharge gaps, the self-induction andone armature of said capacity being arranged in series with and betweena line and an installation to be protected, the other armature of thecapacity being connected to earth, and the discharge gaps beingconnected on the one side to difierent points on the self-induction andarmature which is in series with the line and on the other side toearth, while the product of said self-induction and capacity per unit oflength is greater than the product of the self-induction and capacity ofthe line per unit of length, as and for the purposes set forth.

2. An improved apparatus for protecting electric installations fromexcessive acciden- Ill tal voltages comprising in combination a l inggreater, per unit of length, than the combined self-induction andcapacity con- I product of the self-induction and capacity sisting of atubular insulator provided with of the line per unit of length, as andfor 15 an inner metal lining connected to earth and the purposes setforth.

with an outer metal winding arranged in In testimony whereof we havesigned our series with and between a line and an instalnames to thisspecification in the presence lation to be protected, and discharge gapsof two subscribing witnesses.

connected on the one side to different points CARLO FERRARI.

of said outer winding and on the other side MICHELE PIZZUTI.

to earth, the product of the self-induction of the winding and of thecapacity formed E by the latter with the inner metal lining beiWVitnesses ALFONSO MANCINI, NIcoLA GUORINI.

